The present invention relates to cigarettes and other smoking articles, and in particular to cigarettes, which when smoked, yield relatively low levels of incomplete combustion products, generate low amounts of sidestream "tar" and odor, and sustain smolder during FTC smoking conditions.
Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a roll or charge of smokable material, such as shredded tobacco material (e.g., in cut filler form), wrapped in a paper wrapper, thereby forming a so-called "smokable rod". Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the smokable rod. Typically, a filter element includes cellulose acetate tow circumscribed by plug wrap, and is attached to the smokable rod using a circumscribing tipping material.
Typically, cigarettes are employed by the smoker by lighting one end thereof and burning the smokable rod. As such, smoke normally is provided by burning smokable material, which typically is tobacco cut filler. The smoker then receives mainstream smoke (e.g., mainstream tobacco smoke) into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette. As such, the smoker is provided with the pleasures of smoking (e.g., smoking taste, feel, satisfaction, and the like).
During the time that the cigarette is burning, sidestream smoke is generated. Sidestream smoke is smoke which directly enters the atmosphere from the lit end of the cigarette. Sidestream smoke diffuses into the atmosphere, and the characteristic visible nature and odor thereof may be perceived negatively by some individuals. The relative amount of visible sidestream smoke generated by a burning cigarette is related to the amount of sidestream "tar" generated by that burning cigarette. Typical commercially available cigarettes which burn tobacco cut filler, and have lengths of about 84 mm (e.g., having a smokable rod length of about 57 mm and a filter element length of about 27 mm), often yield about 25 to about 35 mg of sidestream "tar" per cigarette. See, Proctor et al, Analyst, Vol. 113, p. 1509 (1988), for an apparatus and technique for determining the sidestream "tar" of a cigarette.
Numerous cigarettes which reportedly yield relatively low levels of visible sidestream smoke have been proposed. See, for example, U.S. Pat. Nos. 4,637,410 to Luke; 4,624,268 to Baker et al; 4,407,308 to Baker; 4,231,377 to Cline et al; 4,420,002 to Cline; 4,450,847 to Owens; 4,108,151 to Martin; 4,225,636 to Cline; 4,433,697 to Cline; 4,461,311 to Mathews et al; and 4,561,454 to Guess.
Through the years, there have been proposed various methods for altering the composition of mainstream tobacco smoke. For example, many tobacco substitute materials have been proposed, and a substantial listing of such materials can be found in U.S. Pat. No. 4,079,742 to Rainer et al. In addition, tobacco substitute smoking materials having the tradenames Cytrel and NSM were introduced in Europe during the 1970's.
Numerous references have proposed articles which generate flavored vapor and/or visible aerosol. Most of such articles have employed a combustible fuel source to provide an aerosol and/or to heat an aerosol forming material. See, for example, the background art cited in U.S. Pat. No. 4,714,082 to Banerjee et al.
Smoking articles which are capable of providing the pleasures associated with cigarette smoking, by heating but not necessarily burning tobacco, and without delivering considerable quantities of incomplete combustion products, are described in U.S. Pat. Nos. 4,714,082 to Banerjee et al; 4,756,318 to Clearman et al; and 4,793,365 to Sensabaugh, Jr. et al. Such smoking articles employ a combustible fuel element for heat generation; and aerosol forming substances positioned physically separate from, and in a heat exchange relationship with, the fuel element. During use, heat generated by the fuel element acts to volatilize the aerosol forming substances, thereby providing an aerosol which resembles tobacco smoke. Such smoking articles yield extremely low levels of visible sidestream smoke as well as low levels of FTC "tar".
It would be desirable to provide a good tasting cigarette which provides good smoking satisfaction, provides relatively low mainstream gas phase yields, provides relatively low levels of incomplete combustion products, sustains smolder during FTC smoking conditions, yields an ash having desirable physical characteristics, and generates low levels of sidestream "tar" and hence the low levels of visible sidestream smoke.